1. Field of the Invention
The present invention relates generally to apparatuses utilizing a light emitting semiconductor device, and more particularly, to a logic unit, a noise reducing or canceling apparatus and a light beam scanner.
2. Description of the Related Art
As conventional logic units, one of such a type that a semiconductor such as silicon (Si) is used and data is inputted or outputted the form of electric signal has been dominant. On the other hand, in recent years, an optical computer suitable for parallel processing has received attention. This optical computer, however, has not been of such construction as to process all data by an optical signal. Accordingly, a device for converting an electric signal into an optical signal is required. Presently, however, this electro-optical converter does not have additional functions other than an electro-optical converting function. Thus, the construction such as the electro-otpical converter plus an optical logic unit or an electrical logic unit plus the electro-optical converter is required if some logic operation is actually exerted using light. Accordingly, the logic unit has the disadvantage of being complicate and large in size.
Description is now made of an apparatus for reducing or canceling a noise component included in a signal, for example, before or after data.
In many cases, a signal generated from a mechanical switching point includes a noise component based on chattering or the like. Conventional noise reducing circuits are of various types: one provided with a timer, one provided with a counter and the like. A noise reducing circuit provided with a timer is so constructed as to generate an output signal only if an input signal is continued for a constant time period or more. A noise reducing circuit provided with a counter samples an input signal at constant intervals and performs electrical processing such that an output signal attains a high level if the sampled input signal is at a high level a predetermined number of times or more while attaining a low level if it is at a low level a predetermined number of times or more. However, an electric circuit for performing the above described electrical processing is required in such a conventional noise reducing apparatus. Accordingly, the noise reducing apparatus has the disadvantage of being large in size and complicated.
As apparatuses for scanning a light beam, one using a polygonal mirror as represented by a laser beam printer has being conventionally dominant. A beam scanning method using a polygonal mirror has the disadvantage of low response speed and low positional repeatability because there are mechanically moving parts.